code: def call(self, step):
      result_set = self.steps_data[step.dataframe.step_num]
  
      df, col_names = result_set.to_df_cols()
      col_idx = {}
      tbl_idx = defaultdict(list)
      for name, col in col_names.items():
          col_idx[col.alias] = name
          col_idx[(col.table_alias, col.alias)] = name
          # add to tables
          tbl_idx[col.table_name].append(name)
          if col.table_name != col.table_alias:
              tbl_idx[col.table_alias].append(name)
  
      # analyze condition and change name of columns
      def check_fields(node, is_table=None, **kwargs):
          if is_table:
              raise NotSupportedYet(
                  "Subqueries is not supported in WHERE"
              )
          if isinstance(node, Identifier):
              # only column name
              col_name = node.parts[-1]
              if isinstance(col_name, Star):
                  if len(node.parts) == 1:
                      # left as is
                      return
                  else:
                      # replace with all columns from table
                      table_name = node.parts[-2]
                      return [
                          Identifier(parts=[col])
                          for col in tbl_idx.get(table_name, [])
                      ]
  
              if len(node.parts) == 1:
                  key = col_name
              else:
                  table_name = node.parts[-2]
                  key = (table_name, col_name)
  
              if key not in col_idx:
                  raise KeyColumnDoesNotExist(
                      f"Table not found for column: {key}"
                  )
  
              new_name = col_idx[key]
              return Identifier(parts=[new_name], alias=node.alias)
  
      query = Select(
          targets=step.columns, from_table=Identifier("df_table")
      )
  
      targets0 = query_traversal(query.targets, check_fields)
      targets = []
      for target in targets0:
          if isinstance(target, list):
              targets.extend(target)
          else:
              targets.append(target)
      query.targets = targets
  
      res = query_df(df, query)
  
      return ResultSet().from_df_cols(res, col_names, strict=False)
  
file_path: mindsdb/mindsdb/api/executor/sql_query/steps/project_step.py
imports: from collections import defaultdict
  from mindsdb_sql.parser.ast import Identifier, Select, Star
  from mindsdb_sql.planner.steps import ProjectStep
  from mindsdb_sql.planner.utils import query_traversal
  from mindsdb.api.executor.sql_query.result_set import ResultSet
  from mindsdb.api.executor.utilities.sql import query_df
  from mindsdb.api.executor.exceptions import KeyColumnDoesNotExist, NotSupportedYet
  from .base import BaseStepCall
label_desc: Use image node_id 1 for calling the ProjectStepCall obj's underlying member method code with example usage: obj.call(step) and returns: ResultSet, Identifier, unknown